A Primer on Black Soldier Fly

The first contemporary studies of Black Soldier Flies (Hermetia Illucens) and their larvae were completed by three researchers, Furman, Young and Catts in 1959 (the earliest paper I’ve found to date). They noted that the larvae naturally controlled populations of houseflies. The larvae were left alone until around the 1970’s as researchers began searching for cheaper poultry feeds. Larvae are part of a natural diet for poultry and as researchers examined different fly species and their larvae, Hale examined Hermetia Illucens larvae in 1973. In 1977 Newton, Hale, Vooram and Barker examined their use as a feed supplement for swine. These larvae at the time were known as “latrine” larvae and were naturally found in manure piles of large poultry, pig and cattle operations. Through the 1980’s and 1990’s researchers began to investigate what the larvae were doing there and it was noted that they reduced manure load in addition to naturally controlling populations of house flies which are a disease vector.

Since that time, researchers world-wide have been developing additional information about the larvae as the larvae have been described as native to many areas including most of the Western Hemisphere and the Australian region from Samoa to Hawaii. Black Soldier flies have also been found throughout South America and Asia. In BioSystems Designs own studies they were found to be native to Medellín, Colombia.

The larvae themselves are quite hardy. They reportedly can be fully submerged in rubbing alcohol for up to an hour without negative effects. Little literature is available regarding optimum Ph; however, cited in a paper by Dr. Newby is the following: “The larvae tolerate a wide range of pH and will survive well in compost derived exclusively from decomposing citrus fruits (Brues 1928).”
Despite surviving in difficult conditions as larvae, the mature flies are weak fliers and do not venture inside houses or structures. Additionally, they do not bite as they have no functioning mouth parts and consume no food as emerged flies. As adult flies they only live 8-9 days, require only water, and survive off body fat stored in the larval stage. For these reasons, they are not a vector of disease as many flies including the common housefly are. In fact, as discussed earlier, Hermetia Illucens have been found to repel common pests such as the housefly in commercial poultry operations.

Additional advantages to using the larvae include that they have been found to reduce harmful bacteria in organic wastes such as manure and when manure has been used as a larvae feed substrate they have been found to reduce manure mass by 50%, and total nitrogen concentration by 62%. This is important because when left untreated excess nitrogen from manure is a water supply contaminant. In addition, their rapid consumption and aeration of the substrate has been found to reduce odors and therefore presumably methane formation and off-gassing. This latter fact means that an industrial process using black soldier fly to treat manure would be eligible for carbon sequestration credits. In the carbon trading market, methane is considered twenty three times more potent than carbon as a green house gas and therefore one ton of sequestered methane is worth twenty four tons of sequestered carbon. This could prove to be an important source of revenue for a larvae cultivation process. However, additional research to determine the extent to which methane sequestration occurs is required before the credits can be certified and traded and that is outside the scope of this study.

At present, researchers have begun to examine the use of black soldier flies as a fish feed due to the need to find a replacement for fishmeal in animal feeds. While flies are part of a fish’s natural diet, little work had been previously done on larvae-meal as a fish feed or a substitute product for fishmeal. To date, studies of fish species fed black soldier fly larvae have only been performed with rainbow trout, Oncorhynchus mykiss ; channel catfish, Ictalurus punctatus ; and blue tilapia, Oreochromis aureus. This initial research has shown that in the case of rainbow trout, the larvae can replace 25% of fishmeal use and 38% of fish oil use with zero adverse effects. Thus, the larvae are a near perfect substitute. However, much research remains to be done as there is significant room to improve the larvae further as a feed. For example, in the article by St. Hilaire et al 2007, manure fed larvae do not have a high percentage of long-chain unsaturated fatty acids generally desirable for carnivorous fish. However, the authors note that feeding larvae different substrates is likely to affect the larvae composition. For example, in one study where larvae were fed fish offal compared to larvae fed manure, lipid content of the larvae increased 30% and omega-3 fatty acids increased 3%, both increases were within twenty four hours.

Black soldier fly larvae grown on municipal food wastes have so far not been studied by anyone other than BioSystems Design, or if they have no published data has been found by this author. To date, larvae have only been fed manure, fish offal, coffee waste and controlled diets of processed feeds for scientific research. This is a critical area for future research as few options are presently available to food waste producers such as groceries, warehouses, schools and corporate campuses for the environmental treatment of food wastes. In the United States, food waste producers often pay a premium for environmental treatment of the wastes in order to maintain a green public image.

Future research by BioSystems Design will continue to focus on consumption rate of the mixed food waste substrate by the larave, and the resulting biomass and protein development. The purpose of this is to begin to analyze what food wastes the larvae can consume and which food wastes result in optimum growth versus diminished growth or death. The academic community along with BioSystems Design will be investigating Black Soldier Fly larvae as a source of chitin and as a feed for different fish species in different stages of development. This latter research aim is complicated by the fact that fish species respond differently to different types of feeds (specifically the fats, oils, and amino acids in the feed) and need different levels of fats, oils and amino acids at different stages of development. Making the research more interesting is that larvae fed different feeds may have different compositions. BioSystems Design is in the long process of determining the compositions as a result of feed substrate.

Regarding Chitin extraction, additional future studies of black soldier fly larvae are likely to investigate the chitin levels of the larvae as it is theorized that chitin in the larvae exoskeleton may cause a slightly higher feed conversion ratio (gram fed/gram weight gained) as the chitin is indigestible. However, this same Chitin has a relatively high market price ($10-$1000/kg depending upon quality) and extraction of the chitin from the larvae as an industrial process could become an additional revenue stream. This is already the case for the shrimping industry in many nations including Newfoundland. Applications for Chitin include waste-water treatment to bond to heavy metals as it is insoluble in nearly all solvents, chitin as a vehicle for drug delivery, film for fruit preservation, and fiber structures for wound and burn dressing.

Black Soldier Fly Cultivation:

The following represents the “nuts and bolts” facts relevant to Black Soldier Fly cultivation which were found buried inside of research texts. The key distinguishing factor is that they are organized by environmental considerations (in bold). Where inconsistencies are found they are noted. Assistance, suggestions, along the lines of additional sources, inconsistencies, and added environmental considerations are highly welcome. I hope to make this a very active post.

Links to the direct online texts quoted are posted at the bottom of the page when available. Links to this page in appreciation of the work put in to compile the research are very much appreciated.

Optimum Temperatures

Optimum for Mating: “Adults typically mated and oviposited at temperatures of 24 C (75.2 F) up to 40 C (104 F) or more. Booth and Sheppard (1984) reported that 99.6% of oviposition in the field occurred at 27.5 C to 37.5 C (81.5 F to 99.5 f)” (10).

Minimum w/Survival: temperatures as low as 0 C (32 F) for up to 4 hours. (1)

“Larval activity and growth slowed considerably as the mean daytime temperature dropped below 25 C (77 F) (April-September). Observations indicated that larvae seldom pupated at such temperatures. However, after transfer to 30 C (86 F), some of the larvae used in the sludge processing experiments (see below) then pupated and adults later emerged.” (3)

Inconsistencies Discovered: none at present

Crawloff Rate / Bio-Conversion

(also bio-conversion of organic waste to larvae)

“High insect yield: 8% by dry weight – i.e., similar to earthworm systems” (Note: Listed as an advantage to using Hermetia Illucens, however the reference is unclear as to the substrate quantity added). (3)

Presentation by Dr. Paul Olivier is that bio-conversion of food waste done in Bio-Pods in Vietnam was: “roughly 20% by weight of the fresh food waste converted into fresh larvae. This food waste had an average dry matter content of 37%, and the prepupae had an average dry matter content of 44%. On a dry matter basis, the bioconversion of food waste situates at almost 24%.” (4)

Inconsistincies Discovered: Based on the above variance of substrate or study shows a degree between 7.8% (d.m basis) and 24% (d.m. basis). A more conclusive study showing substrate matter is probably required to get an idea of what is causing the actual difference between the bio-conversion of the larvae

Optimum Ph

“The larvae tolerate a wide range of pH and will survive well in compost derived exclusively from decomposing citrus fruits. This finding is consistent with published data where one species of Stratiomyidae was found in water at pH 5.7″ (Brues 1928).(1)

Inconsistencies Discovered: none at present

Optimum Feed(s)

“While the larvae consumed all types of vegetable foods (both natural and processed) they had a limited ability to remove animal products (meat and fat) even when these represented less than 10 percent of the food available in the laboratory.” (1)

Confirmed: A BioSystems Design Study with Universidad de la Salle and Victoria Gutierrez Baron and Natalia Sanchez confirmed that optimum feed for BSF was comprised of 50% vegetable matter and 50% fruit matter, even when compared to a feed of 47.5% vegetable matter, 47.5% fruit matter, and 5% animal products (meat/fat).

Inconsistencies Discovered: none at present

Optimum Humidity

Larval Stage Optimum:

“The larvae tolerate saturated conditions well but large larvae lose weight at approximately 1% per hour at 75.5% relative humidity. As expected, the rate of water loss increases with decreasing relative humidity. Smaller larvae are more susceptible to water loss, losing approximately 1.5% body weight per hour at 75.5% RH.” (1)

“Found that the maximum development rates for soldier flies in dung occurs at 70 % moisture levels.”(1)(2)

Optimum Natural Environment Considerations

“Wet substrates were less attractive to ovipositing Hermetia Illucens (aka black soldier fly) (Booth and Sheppard 1984). Therefore, water was added to medium used for an oviposition attractant to near the saturation point to encourage oviposition… [in another location].” (10)

“Based on observations made at Caboolture Sewage Treatment Plant, soldier flies do not lay their eggs in sewage sludge piles…. Under experimental conditions indoors (described below), adults did not lay in open containers of sewage sludge.” (3)

Additional Considerations:

“Larvae can operate 6 to 8 inches below the surface. At lower depths they accomplish very little bioconversion.” (7)

Inconsistencies Discovered: none at present

Control of Other Insects

“The black soldier fly (BSF) is a southern native, non-pest fly that unlike the house fly, is not attracted to human habitation or foods (Furman et al. 1959). BSF reduce manure accumulations 42-56% and give 94-100% house fly control through larval competition and by repelling ovipositing house flies (Bradley and Sheppard 1984). Elimination of lesser mealworm has been noted, but not well documented. The digested residue is a friable compost-like material with about 24% less nitrogen (net loss of 60%). From Bradley and Sheppard 1984 (6), cited in Roeder Meyer (8)

Special Environmental Affinities

Annex 1: If You’re Interested in How Others Have Grown Black Soldier Fly

This step by step process is written up weekly by author “GW,” aka “The Lord of the Flies” over more than a year. The Pond Boss Forum’s thread on Black Soldier Fly details how “GW” started his Black Soldier Fly colony, lessons he learned to control humidity, uses of different feeds (dog food, hog-feed, coffee grinds, etc), optimum sunlight, and also includes some great video, photos, and humor which makes reading the 15 pages of posts a delight. Also, remember that if you’re looking for something specific ctrl+F is your friend!

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